Planar pressure-responsive elements

ABSTRACT

Pneumatic instrumentation apparatus of the planar type comprising a laminar sandwich construction one layer of which is a stiffly-flexible metal plate formed with cut-out openings to define an interior flat operator pivotally and sealingly supported at intermediate pivot axis region. The operator includes two separate but integral sections, located on opposite sides of the pivot axis. One of these sections is sub-divided into a plurality of separate side-by-side segments each integral with the pivot axis region, and arranged to supply separate torques to such pivot axis, or to move therewith in response to forces applied by other segments of the operator. Such multisegmented pivotable operator is embodied in a variety of instruments, including process controllers, a ratio unit, and a digital-to-analog converter.

United States Patent 1 Prescott PLANAR PRESSURE-RESPONSIVE ELEMENTS [75] Inventor: Robert C. Prescott, Foxboro, Mass.

[73] Assignee: The Foxboro Company, Foxboro,

Mass.

[22] Filed: Feb. 2, 1972 21 Appl. No.: 222,934

Related US. Application Data [63] Continuation-impart of Ser. No. 163,951, July 19,

l97l, Pat. NO. 3,717,]62.

Joy 137/85 1 1 May28, 1974 3,590,694 7/1971 Prescott ct al 137/82 X Primary Examiner-Edgar W. Geoghegan Assistant Examiner-Abraham Hershkovitz Attorney, Agent, or Firm-Bryan, Parmelee Johnson & Bollinger [57] ABSTRACT Pneumatic instrumentation apparatus of the planar type comprising a laminar sandwich construction one layer of which is a stiffly-flexible metal plate formed with cut-out openings to define an interior flat operator pivotally and sealingly supported at intermediate pivot axis region. The operator includes two separate but integral sections, located on opposite sides of the pivot axis. One of these sections is sub-divided into a plurality of separate side-by-side segments each integral with the pivot axis region, and arranged to supply separate torques to such pivot axis, or to move therewith in response to forces applied by other segments of the operator. Such multi-segmented pivotable operator is embodied in a variety of instruments, including process controllers, a ratio unit, and a digital-toanalog converter.

18 Claims, 20 Drawing Figures PATENTEDIM 28 m4 SHEU 2 (If 6 PATENTEDm 28 um SHEET 3 [IF 6 PAIENTEBm as an All PLANAR PRESSURE-RESPONSIVE ELEMENTS RELATED APPLICATION Basic aspects of this invention are disclosed in copending application Ser. No. 163,951 (issued as U.S. Pat. No. 3,717,162) filed by the present applicant on July 19, 1971, and the benefit of the filing date of that application is hereby claimed for this continuation-inpart application.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to pneumatic instrumentation apparatus for industrial processes. More particularly, this invention relates to force and pressure-responsive devices, and especially to improvements in fluidoperated devices of the so-called planar type.

2. Description of the Prior Art Planar-type pneumatic devices typically comprise a v multi-layer laminar sandwich structure one layer of which includes a thin, flat, stiftIy-flexible operator element mounted for pivotal or hinged movement about an axis in the plane of the operator. One or more portions of the operator may be arranged to receive variable forces or pneumatic pressures, and a sensing element, such as a pneumatic nozzle, ordinarily is incorporated to detect changes in the operators position responsive to changes in the applied forces or pressures. The signal developed by the sensing device can be used as a feedback signal for controlling the force on another portion of the operator element, or can be used as an output signal to be transmitted to other apparatus in the instrument system.

In some such planar-type devices, the pivotable operator is formed by etching a flat piece of metal, e.g., with a generally U-shaped opening defining an interior tongue-like operator element pivotally supported at one end, in cantilever fashion, as shown in U.S. Pat.

No. 3,593,734. In another class of such planar devices,

the operator element is pivotally supported at a sealing region dividing the operator into two separate sections; thus the operator serves somewhat in the nature of a balance beam or teeter board, as shown, for example, in U.S. Pat. No. 3,590,694. In either typeof device, the laminar structure includes a number of additional layers extending along both sides of the planar operator to serve various additional purposes such as to define pressure chambers, to establish required pressure seals for such chambers, and to provide interconnecting conduits between pressure chambers, to provide pneumatic restrictor elements in such conduits, etc.

SUMMARY OF THE INVENTION The present invention is directed particularly to furnishing such planar-type devices with enhanced capabilities, while retaining the advantages of simplicity and manufacturing economies inherent in such devices. In an important primary aspect of the present invention, one section of a pivoted planar operator is divided into a plurality of separate side-by-side segments, all on the same side of the pivot axis region and integral therewith, and with each segment being individually movable or controllable. Thus, any one of a number of different such segments are linked by a common pivot axis, so as to move therewith, or to apply separately controllable forces thereto for summing purposes. In

another important aspect of the, present invention, a plurality of individually pivotable balance beam operators are arranged end-to-end, with adjacent ends connected along a common seal line by flexible'diaphragmlike means such that the connected ends are constrained to move together as the planar operators move pivotally about their respective axes. Various constructional arrangements are also disclosed herein to illustrate specific applications of the invention to process instrument functions such as process control, ratioing and digital-to-analog conversion. Other aspects, objects and advantages of the invention will in part be pointed out in, and in part apparent from, the following description considered together with the accompanying drawings.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a planar operator element forming part of a pneumatic process controller;

FIG. 2 is a partial vertical section showing elements of the planar pneumatic device of FIG. 1;

FIGS. 3A through 31 show in perspective individual layers of the laminar structure of the overall controller including the planar operator of FIG. 1;

FIG. 4 is a horizontal section of a ratio unit based on the present invention;

FIG. 5 is a longitudinal vertical section (partly in schematic) taken along line 5-5 of FIG. 4;

FIG. 6 is an enlarged detail section view of the pneumatic switch;

FIG. 7 is a cross-section (partly in schematic) taken along line 7-7 of FIG. 4;

FIG. 8 shows, in longitudinal sectional outline, a modified construction based on the ratiounit of FIG. 4, but arranged for application as an industrial process controller;

FIG. 9 is a cross-sectional outline of the device of FIG. 7;

FIG. 10 shows, in cross-section, a modified form of apparatus providing precisely controlled force from a bendable planar segment;

FIG. 11 is a horizontal section view of an end-to-end arrangement of pivoted planar operators; and

FIG. 12 is a longitudinal vertical sectional outline of the device of FIG. 11.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. 1, there is shown in schematic outline a pneumatic process controller including a flexure assembly generally indicated at 10. This asplates 12A, 128 provided with aligned cutout' sections or openings so arranged as to define a multi-segmented pivotable operator l4 and an elongate element 16 hingedly supported in cantilever fashion at one end 18.

A thin rubber sealing diaphragm '20 is secured. between the two metal plates 12 A, 128. This diaphragm extends across the cut-out openings in the plates to seal off and thereby isolate the pressures on opposite sides of the flexure assembly while permitting small movements of the pivotable operator 14 about its pivot axis 22, and similarly permitting small movements of the hinged element 16 about its cantilever support 18. Cutout 17 is provided to fix an appropriate springiness for such movements of element 16.

FIG. 1 also includes pictorial representations of conduits and the like to indicate the manner in which the various parts of the process controller cooperate and pneumatic pressure signals between the pressure chambers and various operating parts.

The pivotable operator 14 comprises two sections on opposite sides of the pivot axis 22, with one section consisting of a single, relatively large-area tongue-like segment 30 below the pivot axis, and the other section including two smaller separate tongue-like segments 32, 34 above the pivot axis. Each of the operator segments is integral with the common pivot axis region, so as to be movable therewith, or to allow transmittal of separately controllable torsional forces (torques) thereto. As will be explained hereinbelow in more detail, the operator 14 forms part of a force-balance arrangement, wherein the torques applied to the pivot axis region are automatically maintained in balance.

A small rectangular isolation cut-out 36 is formed in the lower segment 30 to effectively isolate or decouple the operator 14 from the oppositely-adjoining non-movable (rigidly held) support arm 38 of the outer peripheral portion of the flexure plates 12A, 128. This cut-out extends laterally (i.e.,' parallel to the pivot axis 22) well beyond the side edges of the support arm, and preferably, as shown, reaches points lying opposite the .near side edges of the two independent segments 32, 34

respectively. That is, the isolation cut-out is effectively coextensive with the opposite cut-outs 40 and 42 defining the adjacent edges of segments 32, 34. This is especially advantageous in accommodating the required pivotal movement of the operator, without encountering severe torsional resistance due to the non-movable outside part of the flexure assembly which is held fixedly in place by the walls of the outer casings.

Adjoining layers of the laminar structure (referring now also to FIG. 2) define one pair of pressure chambers 50, 52 adjacent the respective opposite surfaces of v the lower tongue 30, another pair of pressure chambers 54, 56 adjacent the respective opposite surfaces of the right-hand upper segment 34, and a third pair of pressure chambers 58, 60 adjacent the respective opposite surfaces of the hinged element 16.

The flexible sealing diaphragm prevents air flow through the cut-out regions around the pivotable operator l4 and the hinged element '16. Thus the'opposing pressure chambersare effectively sealed to permit independent pressure variations therein. The left-hand upper segment 32 extends out through the sealed pivot region-22 to beyond the outside walls of the laminar structure, i.e., into open space, typically atmospheric pressure. The sealing diaphragm 20 does not extend out into thatarea.

As noted previously, the pivotable operator 14 is a force-balance device; that is, the torques about the pivot axis 22 are maintained in balance by negative feedback action. The feedback signals are developed basically by a pneumatic position-sensing nozzle 62 associated with the external operator segment 32 and connected through an output conduit 64 and a restrictor 66 to the usual air supply source, e.g., at 20 psi. ln essence, the nozzle 62 detects any unbalance in the net torque about axis 22 resulting from differences between two pressures applied to opposite sides of the right-hand operator segment 34 (in respective pressure chambers 54, 56), and between the pressures applied to opposite sides of the lower operator segment 30 (in the respective pressure chambers 50, 52).

The pressure in chamber 56 is the so-called set" pressure, derived from a set pressure conduit 68. The pressure in the opposite chamber 54 is the measurement pressure, derived from conduit 70 leading to a conventional measurement instrument (not shown) such as a differential-pressure cell or the like. The pressures in chambers 50, 52 are controlled by pneumatic feedback circuits, to be described, responsive to the position-sensing nozzle 62.

The back-pressure of position-sensing nozzle 62 is directed through conduit 64 to an output relay 72 to produce a corresponding relay signal which serves to activate the feedback circuits mentioned above and 1 also serves as the output (control signal) of the controller, e.g., providing valve positions appropriate for maintaining the measurement and set pressures equal. When the process condition being controlled is stabilized, with measurement and set pressures steady and equal, the torques on the pivotable operator 14 will be balanced with the operator so positioned that the nozzle back-pressure will produce the correct control signal for maintaining the stabilizing valve position.

If the measurement and set signals become unequal,

-the resulting pressure differential between the opposite surfaces of the upper operator segment 34 will develop a torque about the pivot axis 22. This torque will tend to rotate the pivotable operator 14, causing corresponding movement of both the lower tongue 30 and the external segment 32. That is, all of the tongue seg ments are integral and thus tend to move in unison about the common pivot axis. Consequently, the backpressure of nozzle 62 will change, so as to alter correspondingly the output pressure from the relay 72.

This relay output pressure is conducted to a negative feedback conduit 74 leading to the pressure chamber 52 behind the lower tongue 30, and serves to maintain the net torques on the pivoted operator 14 in balance. When the torque is momentarily unbalanced by a change in measurement or set pressures, the resulting change in relay output pressure produces a corresponding change in the feedback pressure in chamber 52 just sufficient to counteract the initial torque unbalance. When balanced conditions are restored, the net output pressure from relay.72 represents the controller output signal for appropriately readjusting the process valve to bring the measurement signal into equality with the set signal.

This controller also includes means for developing a reset function in its output signal. In effect, the control action (opening or closing of the valve) is gradually augmented in response to a persistent deviation between measurement and set signals. This reset is produced by a positive feedback circuit wherein the relay output pressure is conducted through a positive feedback conduit 76 to a variable pneumatic reset restrictor 78. (This restrictor is illustrated as part of a dual restrictor assembly 80, and is presented in the form of a so-called scratch restrictor of known design.) From the outlet 82 of the reset restrictor 78, the reset circuit continues through the usual relatively large-capacity tank or volume 84 and damping restrictor 85 to the lower pressure chamber 60 behind the hinged element 16.

This hinged element 16 is utilized primarily for pneumatic isolation, and serves as a one-to-one (1:1) repeater to produce in the front chamber 58 a pressure equal to the reset pressure in the rear chamber 60. For this purpose, the front chamber 58 is connected through a fixed restrictor 86 to a supply of air under pressure (e.g., 20 psi), and a vent nozzle 88 is mounted in the chamber adjacent element 16 so as to adjust the degree of vent restriction in accordance with the position of the element. If the pressure in the front chamber 58 becomes unequal to the reset pressure in the rear chamber 60, the element 16 will be moved by the resulting pressure differential so as to alter the effective restriction presented by the vent nozzle, and thereby restore balanced pressure conditions. Thus the pressure in chamber 58 will be maintained equal to the reset pressure in the opposite chamber 60.

The repeated reset pressure is coupled from chamber 58 through a pressure-dropping restrictor 90 and a damping restrictor 91 to the pressure chamber 50 in front of the lower tongue 30 of the pivotable operator 14. The pressure in chamber 50 tends to counteract or reduce the negative feedback torque produced by the pressure in the rear chamber 52, and thus can be considered as providing a degree of positive feedback. The dynamics of the positive feedback action depends, as in conventional pneumatic reset circuits, on the setting of the reset restrictor 78, as well as on the magnitudes of other fixed parameters of the reset circuit. At all times, however, the torques on the pivotable operator 14 are maintained in balance by the negative feedback action from the sensing nozzle 62.

The dual restrictor assembly 80 includes a second adjustable scratch restrictor 92 which is connected, by a conduit 93 between the relay output pressure and the fixed pressure-dropping restrictor 90 leading to the repeater output chamber 58. Thus this second restrictor 92 is effectively in series with the fixed restrictor 90, and the two together serve functionally as a pressuredividing network, providing at the juncture 94 between the two restrictors a pressure having magnitude somewhere between the magnitude of the output and reset pressures. The actual magnitude of this positive feedback pressure is a function of the ratio of the fixed and variable reset restrictors 90 and 92. This positive feedback pressure is directed through the damping restrictor 91 to the positive feedback chamber 50. Thus it will be evident that the degree of proportioning action is controlled by the setting of the adjustable restrictor 92.

Advantageously, the fixed pneumatic restrictors associated with the planar pneumatic controller are small holes formed in the flexure assembly 10. Thus, in FIGS. 3C, 3D and 3E, aligned holes are shown as providing the restrictors identified with the reference numbers used in other portions of this specification. The manner in which such restrictor holes are connected into the associated pneumatic circuits is as describedin US. Pat. No. 3,593,734. Also in accordance with that patented technology, use is made of pneumatic passages formed in the laminar sandwich castings for purposes of effecting desired interconnections. The casting of FIG. 3A also is formed with an enlarged portion 84A to serve as the reset volume 84 associated with the adjustable scratch resistor 78 for setting the degree of reset action.

The restrictor assembly is described in detail in the above-mentioned copending application Ser. No. 163,951, and such description will not be repeated herein.

FIGS. 3A through 31 provide perspective views of the laminar sections which are combined in a sandwich construction to form the controller. The central portion is the flexure assembly 10 which includes the pivotable operator 14. This flexure assembly is similar to the operator shown in the above-identified US. Pat. No. 3,590,694, and comprises the two outer sections 12A, 12B of thin springy metal, adhesively secured (as by epoxy) to corresponding sides of the mating rubber sealing diaphragm 20. Adjacent opposite sides of the flexure assembly are respective sealing gaskets 95, 96.

These gaskets 95, 96 furnish required pressure seal ing for the top casting 97, on one side, and the base sandwich 98 on the other side. This base sandwich comprises a chamber casting 98A adhesively secured to a thin cover plate 983 which serves to seal various pneumatic passages formed in the remote side of the chamber casting to define pressure conduits somewhat in the fashion that such pressure conduits are formed in the pneumatic computing apparatus disclosed in US. Pat. No. 3,371,862 issued to H. L. Bowditch et al.

The final section of the laminar sandwich construction is a relatively rigid base plate 99 provided with access openings to make connections between the controller and other elements of the control system. These access openings incorporate rubber O-rings inserted therein to seal the connections between the controller and the pneumatic circuit board (not shown herein) to which this controller is secured, in accordance with the techniques described in copending application Ser. No. 864,108, filed on Oct. 6, 1969, issued as U.S. Pat. No. 3,631,881 by I-Ioel L. Bowditch.

Referring now to FIG. 4 through 7, there is shown another force-balance planar device, in this case arranged to produce an output signal the magnitude of which bears a predetermined (but adjustable) ratio with respect to a variable input signal. This device comprises a generally rectangular laminar structure one layer of which includes a flexure assembly, generally indicated at 100, comprising two thin, flat sheets 102 of stiffly flexible metal sandwiched together with an intermediate layer 103 of resilient material, such as rubber. Both sheets 102 are identical and are formed, as by stamping or etching, with a series of openings defining an outer peripheral portion and an interior portion comprising a pivotable operator indicated at 104.

One such opening 105 outlines a relatively large, approximately triangular tongue section 106 (FIG. 4) running along one side of the pivot axis region generally indicated at 108. The section of the flexure assembly on the opposite side of the pivot axis region is formed with a plurality of approximately U-shaped openings 110, 112, 114, 116, defining a number (four in this embodiment) of relatively small, side-by-side tongue segments 118, 120, 122, 124 all integral with the large operator section 106. A series of small generally rectangular isolation openings 126, 128, 130 also is'formed in the metal sheets 102 to provide for free pivotal movement of the tongue section 106.

The laminar structure further includes casing members I32, 134 formed with walls 136, 138 serving as pivotal supports for the planar operator 100 about the pivot region 108. As shown in FIG. 4, this pivot axis may, for certain applications, run diagonally across the operator, thereby providing different effective areas for the tongue segments 118 124 in accordance with a predetermined pattern, i.e., decreasing from one end to the other of the pivot axis. The effective areas of the separate tongue segments also are controllable in accordance with the widths thereof, to suit any particular application.

I the planar operator 104, a series of sealed pressure chambers 140, 142,144, 146, 148. Each of these pressure chambers includes an inlet 150, 152, 154, 156, 158 into which a fluid pressure can be admitted to apply a corresponding pressureto the underside of the respective tongue segment.

Four pneumatic switches 160, 162, 164, 166 serve as means for controlling the input to corresponding pressure chambers 142 148 associated with the side-byside tongue segments. These switches are shown as manually-operable, rotary switches (see FIG. 6), simply to illustrate the function involved, but it will be understood that in a commercial embodiment of the invention other types of pneumatic switches, known in the art, ordinarily will be employed. For example, the switches could be included as integral parts of the laminar sandwich structure, e.g., within the outer casing.

Switches 160 166 permit the pressure chamber 142 148 to be connected to, or isolated from, an input pressure line 168 carrying an input signal pressure. Alternatively, in the other switch position, the individual pressure chambers can be selectively vented to atmosphere.

The pressure chamber 140, beneath the large-area operator section 106, includes a pneumatic nozzle 170 the orifice of which is closely adjacent the underside of the operator section which is arranged to serve as a flapper for controlling the effective nozzle opening. The remote end of the nozzle is vented to atmosphere.

Inlet 150 to chamber 140 is connected through a restrictor 172 to a source of air under pressure, e.g., 20 psi. With this arrangement, the pressure in the chamber is controlled by the spacing between the nozzle orifice and the tongue section 106.

The ratio device illustrated in FIGS. 4 through 7 opf erates to produce in an output line 174 an output presline 168, and thereby determines the amount of net input torque developed about the pivot axis 108 by the combined action of the side-by-side tongue segments. This input torque tends to pivot the operator so as to move the large-area tongue section 106 towards the nozzle 170. This tends to increase the restrictive effect of the nozzle, raising the pressure in its chamber 140, and thereby increasing the counter-torque produced by tongue section 106 about the pivot axis. Thus the pressure in chamber is automatically maintained at a level corresponding to the net torque produced by the input pressure, i.e., the negative feedback action maintains a balance of torques.

The selected settings of switches 166 determines the composite (cumulative) input torque produced by the tongue segments 118-- 124 about the pivot axis 108 in response to the input pressure signal in line 168, and the output pressure in line 174 represents (corresponds to) the magnitude of that composite torque. If the input pressure in line 168 changes, there will be a corresponding change in the output pressure, so as to maintain the two pressures in a fixed ratio. By changing the selected switch settings, the composite input torque can be altered (without any change in input pressure), and the feedback action of nozzle will automatically change the output pressure to maintain the torques in balance. Accordingly, the switch settings determine the ratio between the output and input pressures.

By arranging the areas of the tongue segments 118 124 in accordance with a digital weighting pattern, the device can be used as a digital-to-analog converter. For example, the areas can be selected such that each tongue has an area one-half that of the nextpreceding tongue in the series (from one end to the other), thereby providing a conversion from binary-digital input to analog output.

in the embodiment of FIG. 4, pressures are applied only to the lower surfaces of the operator 104, and the spaces above the operator are vented to atmosphere. For some applications, controllable pressures also can be applied to both top and bottom surfaces, thereby increasing the flexibility of the apparatus for a variety of uses. Thus, as shown in FIGS. 8 and 9, controllable pressure chambers 200, 202, 204, 206, 208 may be provided above the respective tongues of the operator.

Such a device may, for example, be used as a process controller, with the individual pressure chambers 142 148 and 202 208 being connectable by respective pneumatic switches 160 166 and 212 218 to either a measurement pressure line 220 (carrying a pressure responsive to a process condition being controlled) or to a set point pressure line 222 (carrying a pressure representing a desired level for the process condition). The output pressure signal at line 174 is, in this case, also connected through a restrictor 224 (and a capacity tank, not shown) to the pressure chamber 200 above the large tongue section 106, thereby to achieve a de layed feedback action producing the process controller effect referred to as reset.

The settings of switches 160 166 and 212 218 determine the'net torque produced by the tongue segments 118 124 in response to a given deviation between measurement and set signals, and thereby determine the magnitude of the initial change in output pressure in line 174 produced by such deviation. Thus, the

switches provide an adjustable proportioning band for the controller.

It may be noted that in a process controller, the measurement pressure tends ultimately to become equal to the set point pressure. When the process is on control, there will be no net pressure differential between the top and the bottom surfaces of the operator 104. Thus,

" atively large strokewhich normally might make it difficult to achieve an accurately controlled torque from the tongue. For digital input applications, where the torque must be either zero or some predetermined constant value, the torque can be controlled to within desirably accurate limits by an arrangement such as shown in FIG. 10.

In this FIG. 10 arrangement, an operator tongue 250 is arranged for a relatively large angular movement between its normal flat zero position, shown in solid outline, to an activated position shown in dotted outline at 250A. At the latter position, further movement of the tongue is prevented by a set screw 252 against which the tongue comes to rest. Thus, even though the applied pressure in the chamber 254 may not be held precisely to a given value, as long as the pressure is sufficiently large, the tongue always will stop at the prese- "lected angular stroke position, producing a precisely controlled torque. The diaphragm 256 in this case includes a slack portion 256A to permit the relatively large angular motion. A second mechanical stop 258 may be provided for the zero position, if desired.

FIGS. 11 and 12 show another planar pneumatic device of laminar construction comprising in one layer a plurality of pivotable operators 300, 302 arranged in an end-to-end configuration, substantially in the same plane. Each operator is sealingly supported at the respective pivot regions 304, 306, and the pivot axes are parallel. The outer casing layers of the device define three pressure chambers 308, 310, 312 above the two operators, and three corresponding chambers 314, 316, 318 below.

The adjacent ends 320, 322 of operators 300, 302 are connected together by a flexible connector 324, e.g., a metallic diaphragm-type element which seals off the pressures above and below the operators while permitting at least small relative angular movements between the two operators. The inter-connected operator ends are, by these means, constrained to move together, with respect to translational movement perpendicular to the effective plane of the two operators.

Five of the pressure chambers 308 316 are supplied with independently controllable pressures through corresponding inlets. The sixth pressure chamber 318 includes a sensing nozzle 330 the orifice of which is adapted to cooperate with the underside of the operator 302. The remote end of the nozzle is vented to atmosphere, and the chamber is supplied with air through the usual pneumatic restrictor 332, so as to produce an output signal in an output conduit 334. Thus, the pressure in the chamber 318 automatically adjusts to whatever value is required to balance the net torque transmitted through pivot seal 306. This also balances the torques about the other pivot seal 304, so that the instrument is maintained in force-balance condition at all of the interconnected planar operators. In the described embodiment, only two such planar operators are illustrated, but there is no theoretical limitation on the number of operators provided, depending, of course, upon the specific application.

A two-operator unit, such as illustrated in FIGS. 11 and 12, may for example be used to minimize the bending deflection of a'pivoted operator which is being employed to rebalance a variable input'force, e.g., a force developed in a differential-pressure flow measuring system. In one such arrangement, the differential pressure could be applied across the central operator regions, i.e., chambers 310, 316, with the pressure difference being detected by the nozzle 330. The output signal from conduit 334 could be applied as negative feedback to the left-hand end 340 of the left-hand operator 300. Thus, that operator, by its connection 324, will restrain the bending deflection of the second operator 302, and thereby minimize any distortion of the output signal which might result from such deflection.

Although several preferred embodiments of the invention have been described hereinabove in detail, it is desired to emphasize that this is for the purpose of illustrating the invention and is not necessarily limiting thereof, it being understood that those skilled in this art will make modifications as required to such particular applications, without departing from the scope of the invention.

1 claim: I

1. In fluid-operated apparatus for use in process instrumentation systems and the like, the combination of:

a pivotable operator;

support means mounting said operator about a pivot axis region separating two adjacent operator sections; one of said operator sections comprising two separate side-by-side segments each integral with said pivot axis region;

the ends of said segments remote from said pivot axis region being independent of one another and individually free to move in response to a torque tending to move the segment about the pivot axis region, whereby either segment can be actuated pivotably about said pivot axis region independently of the other segment.

2. Apparatus as in claim 1, including a wall structure effectively sealing the spaces adjacent one side of one of said segments from the spaces adjacent the other segment, thereby to permit independent variation of fluid pressures acting on said one segment.

3. Apparatus as in claim 2, wherein said wall structure includes first means cooperable with said one segment side to define a pressure chamber for controlling the forces applied to said one segment.

4. Apparatus as claimed in claim 3, wherein said wall structure includes second means cooperable with a side of said other segment to define a second pressure chamber for controlling the forcesapplied to said other segment. V

5. Apparatus as claimed in claim 4,wherein said wall structure includes third means cooperable with the other of said operator sections to define a third pressure chamber for controlling the forces applied to said other operator section.

6. Apparatus as claimed in claim 5, wherein the forces applied to said two separate segments produce torques acting in the same direction about said pivot axis.

7. Apparatus as claimed in claim 5, wherein said third wall structure means is arranged such that the forces applied to said other operator section produce a torque opposing the net torque produced by forces acting on said two separate segments.

8. A force-balance device comprising: an operator; support means mounting said operator for pivotal movement about a pivot axis region between two sections thereof; one of said sections comprising a plurality of separate sideby-side segments the ends of which remote from said pivot axis region are free for independent movement about said pivot axis region and individually actuable to apply corresponding torques to i said pivot axis region, thereby to develop at said region a net torque corresponding to the combination of torques individually applied thereto; and means to apply to said operator a rebalancing force producing at said pivot region a torque counterbalancing said net torque.

9. A device as in claim 8, including wall means defining individual pressure chambers adjacent said separate segments and the other section of said operator, thereby to control the applied forces by controlling the pressures in said chambers.

10. A device as claimed in claim 9, wherein said wall means includes means defining individual pressure chambers adjacent opposite sides of said separate segments. 11. A device as claimed in claim 9, wherein the pressure-responsive areas of said segments are related in a progressive pattern so as to permit obtaining a wide range of possible net torques by selectively actuating different combinations of said pressure chambers.

12. A device as claimed in claim 11, wherein said areas are related in a digital-weighting pattern, thereby to permit digital-to-analog conversion.

13. A device as claimed in claim 8, wherein mechanical stops are provided adjacent each of said segments to limit the travel thereof, thereby to precisely control the torque contribution of the segment.

14. A force-balance device comprising:

a plurality of elongate pivotable operators each having a pivot axis region between opposite operator sections;

means mounting said operators in a laterally adjacent, end-to-end disposition such that the pivot axes thereof are offset laterally and the end of one section of one operator lies laterally adjacent the end of one section of the next operator in the series;

means connecting said adjacent section ends to effect correspondence in the movement thereof as the operators pivot about their respective axis; and means to apply forces selectively to said operator sections.

15. In fluid-operated apparatus for use in process in- I strumentation systems and the like, the combination of:

a pivotable operator including first and second sections on opposite sides of the pivot axis;

one of said sections comprising a pair of side-by-side independently actuable segments each integral with the pivot axis region and having the ends thereof remote from said region arranged for individual movement about the pivot axis, the other section extending laterally along the pivot axis through a region opposite both of said segments;

said other section being formed with an isolation cutout adjacent the pivot axis region and located op- V posite the portion of said one section which lies between said two segments.

16. Apparatus as claimed in claim 15, wherein said operator forms part of a sheet of stiffly-flexible material formed with separate openings defining said segments and said other section respectively, whereby a portion of said sheet is disposed between said two segments;

said isolation cut-out being located in the pivot axis region lying opposite said sheet portion and extending laterally along the axis to regions lying opposite the adjacent side edges of said segments.

17. Apparatus as claimed in claim 16, wherein said operator forms part of a sandwich structure including an outer casing comprising wall means defining pressure chambers for at. least one of said segments, said wall means being sealingly engaged with said sheet por-. tion lying between said two segments and holding that sheet portion firmly in place;

said isolation cut-out opening serving to decouple said other operator section from said firmly held sheet portion so as to permit relatively free pivotal movement of said other section about said pivot axis.

18. For use with industrial process instruments and the like, laminar fluid-responsive apparatus comprismg:

a flexure assembly formed with an opening defining an outer portion and an interior portion comprising a pivotable operator section integral with said outer portion at a pivot region;

said operator section being divided into at least two separate independently movable side-by-side segments each individually integral with the pivot region;

a wall structure defining at least one pressure chamber adjacent a respective portion of said operator, said wall structure serving also as a pressure-sealing barrier between said separate segments; and,

means to apply torque-producing pressure to one of said separate segments independently of the application of pressure to the other of said segments. 

1. In fluid-operated apparatus for use in process instrumentation systems and the like, the combination of: a pivotable operator; support means mounting said operator about a pivot axis region separating two adjacent operator sections; one of said operator sections comprising two separate side-byside segments each integral with said pivot axis region; the ends of said segments remote from said pivot axis region being independent of one another and individually free to move in response to a torque tending to move the segment about the pivot axis region, whereby either segment can be actuated pivotably about said pivot axis region independently of the other segment.
 2. Apparatus as in claim 1, including a wall structure effectively sealing the spaces adjacent one side of one of said segments from the spaces adjacent the other segment, thereby to permit independent variation of fluid pressures acting on said one segment.
 3. Apparatus as in claim 2, wherein said wall structure includes first means cooperable with said one segment side to define a pressure chamber for controlling the forces applied to said one segment.
 4. Apparatus as claimed in claim 3, wherein said wall structure includes second means cooperable with a side of said other segment to define a second pressure chamber for controlling the forces applied to said other segment.
 5. Apparatus as claimed in claim 4, wherein said wall structure includes third means cooperable with the other of said operator sections to define a third pressure chamber for controlling the forces applied to said other operator section.
 6. Apparatus as claimed in claim 5, wherein the forces applied to said two separate segments produce torques acting in the same direction about said pivot axis.
 7. Apparatus as claimed in claim 5, wherein said third wall structure means is arranged such that the forces applied to sAid other operator section produce a torque opposing the net torque produced by forces acting on said two separate segments.
 8. A force-balance device comprising: an operator; support means mounting said operator for pivotal movement about a pivot axis region between two sections thereof; one of said sections comprising a plurality of separate side-by-side segments the ends of which remote from said pivot axis region are free for independent movement about said pivot axis region and individually actuable to apply corresponding torques to said pivot axis region, thereby to develop at said region a net torque corresponding to the combination of torques individually applied thereto; and means to apply to said operator a rebalancing force producing at said pivot region a torque counter-balancing said net torque.
 9. A device as in claim 8, including wall means defining individual pressure chambers adjacent said separate segments and the other section of said operator, thereby to control the applied forces by controlling the pressures in said chambers.
 10. A device as claimed in claim 9, wherein said wall means includes means defining individual pressure chambers adjacent opposite sides of said separate segments.
 11. A device as claimed in claim 9, wherein the pressure-responsive areas of said segments are related in a progressive pattern so as to permit obtaining a wide range of possible net torques by selectively actuating different combinations of said pressure chambers.
 12. A device as claimed in claim 11, wherein said areas are related in a digital-weighting pattern, thereby to permit digital-to-analog conversion.
 13. A device as claimed in claim 8, wherein mechanical stops are provided adjacent each of said segments to limit the travel thereof, thereby to precisely control the torque contribution of the segment.
 14. A force-balance device comprising: a plurality of elongate pivotable operators each having a pivot axis region between opposite operator sections; means mounting said operators in a laterally adjacent, end-to-end disposition such that the pivot axes thereof are offset laterally and the end of one section of one operator lies laterally adjacent the end of one section of the next operator in the series; means connecting said adjacent section ends to effect correspondence in the movement thereof as the operators pivot about their respective axis; and means to apply forces selectively to said operator sections.
 15. In fluid-operated apparatus for use in process instrumentation systems and the like, the combination of: a pivotable operator including first and second sections on opposite sides of the pivot axis; one of said sections comprising a pair of side-by-side independently actuable segments each integral with the pivot axis region and having the ends thereof remote from said region arranged for individual movement about the pivot axis, the other section extending laterally along the pivot axis through a region opposite both of said segments; said other section being formed with an isolation cut-out adjacent the pivot axis region and located opposite the portion of said one section which lies between said two segments.
 16. Apparatus as claimed in claim 15, wherein said operator forms part of a sheet of stiffly-flexible material formed with separate openings defining said segments and said other section respectively, whereby a portion of said sheet is disposed between said two segments; said isolation cut-out being located in the pivot axis region lying opposite said sheet portion and extending laterally along the axis to regions lying opposite the adjacent side edges of said segments.
 17. Apparatus as claimed in claim 16, wherein said operator forms part of a sandwich structure including an outer casing comprising wall means defining pressure chambers for at least one of said segments, said wall means being sealingly engaged with said sheet portion lying between said two segMents and holding that sheet portion firmly in place; said isolation cut-out opening serving to decouple said other operator section from said firmly held sheet portion so as to permit relatively free pivotal movement of said other section about said pivot axis.
 18. For use with industrial process instruments and the like, laminar fluid-responsive apparatus comprising: a flexure assembly formed with an opening defining an outer portion and an interior portion comprising a pivotable operator section integral with said outer portion at a pivot region; said operator section being divided into at least two separate independently movable side-by-side segments each individually integral with the pivot region; a wall structure defining at least one pressure chamber adjacent a respective portion of said operator, said wall structure serving also as a pressure-sealing barrier between said separate segments; and, means to apply torque-producing pressure to one of said separate segments independently of the application of pressure to the other of said segments. 